A “multi-homed” communications network is one in which there are two or more address domains, those address domains being connected by two or more nodes which allow address translation between those domains. For example, the nodes which allow address translation may be any suitable type of network address translator (NAT) as is known in the art.
An “address domain” is a region of a communications network in which each network node has an address or identifier which is unique within that region and which is allocated on the basis of a particular method or scheme. For example, the same address may be repeated between two different address domains but not within a single address domain.
When a call is set up, for example in a voice over internet protocol (VoIP) network or a voice over ATM (asynchronous transfer mode) communications network, call signalling occurs between the originating party and the destination party. This also applies when the call involves other media such as video or data instead of or in addition to voice. As a result of this call signalling, in an internet protocol (IP) network, a media path is set up in the reverse direction from the destination party to the originating party. This process also occurs in the other direction such that a media path from the originating party to the destination party is also set up. In an ATM network, after the initial signalling, further signalling occurs as a result of which a bi-directional media path between the parties is set up.
The present invention is concerned with situations in which the call signalling follows an indirect path between the originating party and the destination party. Such an indirect path can occur because of the multi-homed nature of the communications network and the need for the signalling to be routed via entities in the other addressing domain(s), in order to access services provided by those entities (such as routing services provided by Call Servers). Previously, in this type of situation, the resulting media paths also follow an indirect path through the other addressing domain(s). The media may not follow the exact same path as the signalling in that the media will not go through the Call Servers, but it will go through the same sequence of networks. This is wasteful of network resources, increases complexity, reduces voice quality and adds to expense.
The invention seeks to provide an improved method and apparatus for establishing a communications path between a first and second entity in a multi-homed communications network which overcomes or at least mitigates one or more of the problems noted above.
Further benefits and advantages of the invention will become apparent from a consideration of the following detailed description given with reference to the accompanying drawings, which specify and show preferred embodiments of the invention.